Jackie started his career at Bairns' rivals Dunfermline Athletic for four seasons and then joined Celtic in 1995 for £650,000. In 1996, he was named Scottish PFA Young Player of the Year and the following year, he won his first SPL Championship. In 2004, he was awarded the Football Writer's Player of the Year. McNamara played 255 games for Celtic and scored 10 goals. 

For the national team, Jackie was the no.2 in Scotland's 1998 World Cup campaign. He played over 30 games for Scotland.

McNamara left for Wolverhampton Wanderers in 2005 but 2 years later, he signed for Aberdeen. After playing just 1 season for the Dons out of position, Jackie opted to join the Bairns in Summer 2008.